Advancements in display technology, including the development of plasma display panels (PDPs) and plasma addressed liquid crystal (PALC) displays, have led to an interest in forming electrically-insulating ceramic barrier ribs on glass substrates. The ceramic barrier ribs separate cells in which an inert gas can be excited by an electric field applied between opposing electrodes. The gas discharge emits ultraviolet (uv) radiation within the cell. In the case of PDPs, the interior of the cell is coated with a phosphor which gives off red, green, or blue visible light when excited by uv radiation. The size of the cells determines the size of the picture elements (pixels) in the display. PDPs and PALC displays can be used, for example, as the displays for high definition televisions (HDTV) or other digital electronic display devices.
One way in which ceramic barrier ribs can be formed on glass substrates is by direct molding. This has involved laminating a planar rigid mold onto a substrate with a glass- or ceramic-forming composition disposed therebetween. The glass- or ceramic-forming composition is then solidified and the mold is removed. Finally, the barrier ribs are fused or sintered by firing at a temperature of about 550° C. to about 1600° C. The glass- or ceramic-forming composition has micrometer-sized particles of glass frit dispersed in an organic binder. The use of an organic binder allows barrier ribs to be solidified in a green state so that firing fuses the glass particles in position on the substrate. However, in applications such as PDP substrates, highly precise and uniform barrier ribs with few or no defects or fractures are required. These requirements can pose challenges, especially during removal of the mold from the green state ribs and during firing of the green state ribs.
Mold removal can damage ribs due to difficulty in mold release. Because barrier ribs tend to shrink during firing, the green state ribs must be taller than the size desired for the fused ribs. Taller structures make demolding even more difficult. Mold removal can also damage the mold. When material cannot be completely removed from the mold, the mold must be discarded. In addition, at temperatures required for firing, the barrier ribs can fracture, delaminate from the substrate, or warp. The substrate also goes through dimensional changes during firing due to thermal expansion and release of internal stresses.